1. Field of the Invention
The present invention relates to a tool for use in manufacturing a metal-fiber web-sintered body such as a filter, and more specifically, relates to a separating plate which separates a web so that the webs do not attach to each other when laminating and sintering a web to be sintered.
2. Description of the Related Art
A metal-fiber web-sintered body such as a filter is produced to have a diameter of about 10 to 40 xcexcm by pressurizing and heating in a furnace a web of a metal fiber, such as a stainless-steel metal fiber. Upon this production, it is customary to produce simultaneously a plurality of web-sintered bodies by laminating a plurality of webs. In this case, the pressurization and heating treatment is carried out with a separating materials arranged between the webs so that the vertically adjacent webs are not sintered in a contacting condition. The characteristics required for such a separating material is as follows. It is required that the vertically arranged webs can separate, that the separating material has a heat resistance, and that the web and the separating material do not adhere to each other.
Conventionally, as such a separating material, there has been used a Fexe2x80x94Cr alloy plate. In this case, an Al2O3 (alumina) film is formed on the surface of the alloy plate by heat-treating the Fexe2x80x94Cr alloy plate at a predetermined temperature. The alumina film is good in heat resistance and has a low reactivity with a web, and thus, it is possible to properly separate the web. However, there are problems such that the Fexe2x80x94Cr alloy plate is expensive, and that according to this method, the heat treatment has to be sufficiently controlled.
Further, as materials which use alumina and are good in separatability, there have been used an alumina-fiber paper material produced by carding alumina fibers, or a sheet-like material formed by weaving a string of alumina fibers. However, when materials using alumina fibers are used, the alumina fibers adhere to the web, causing problems such as deterioration in the quality of the web and shortening of durable life.
Accordingly, an object of the present invention attempts to achieve is to provide a separating material used during sintering which is inexpensive and is superior in separatability.
An aspect of the present invention is a separating material for web sintering which comprises a substrate and an alumina film formed by thermal spraying alumina to the substrate. The thickness of the alumina film is 30 xcexcm or more, and preferably in the range of from 40 to 70 xcexcm. If the alumina film is below 30 xcexcm, there is a tendency that the thermal spray film will become uneven; if it is over 70 xcexcm, there is a tendency that exfoliation will occur within the film.
As for the substrate, a carbon plate which is good in heat resistance and shape stability may be used, and preferably, it is possible to increase the strength thereof by using a carbon plate which is reinforced by a carbon fiber. In this case, it is possible to make the thickness of the carbon plate thinner compared to the conventional carbon plate, and further, it will be possible to effectively increase its strength by orienting the carbon fiber. Further it is possible to use a stainless-steel plate, which is more inexpensive. Also, it is possible to use a wire gauze, such as a stainless-steel wire gauze, as a substrate. In this case, there is an advantage in that it is possible to degas a gas which is generated from the web during web sintering.
In the web separating plate of the present invention, since alumina is thermal sprayed, there is a feature that thermal spraying is applicable to a wide variation of materials for substrates. Further, since a film is formed by this thermal spraying, it is possible to freely select the thickness of the film. Further, since this is a metal film, there is no conventional drawback in that a fiber, such as a metal fiber, will fall off.
An SiO2 component may be added to the alumina to be thermal sprayed, according to the characteristics required for the film. Further, it is possible to add, for example, TiO2 or ZrO2 in order to strengthen the contact between the alumina and the substrate.
As for the material of the substrate, a ceramic may be used, which is good in heat resistance and shape stability. Examples thereof may includes a carbon plate, a carbon plate reinforced with a carbon fiber, and the like. As for the other substrates, a metal material of which shape is easy to process may be used; and it is possible to use a stainless-steel, and a titanium-metal which is good in both heat resistance and corrosion resistance.
When using a metal material, if the substrate is made to have a wire gauze shape, it will become possible to degas the gas generated from a web during treatment by pressurization and heating, and it will become possible to prevent a deterioration in quality caused by gas generation. This is because when using a metal material, there is a problem that if the generated gas is not degassed, a discoloration of the sintered body will occur because of oxidization, and a decrease in strength will be caused because of embrittlement of metal fiber.